Impedance Diagram of Low Pass Filter

A proper answer requires more information about the filter than "low pass". For one thing, phase is a relative measure. You must describe what your reference is and where you want the angle. A drawing would help.

Jerry

Presuming a RC ladder section Item 1 is correct if you drop i in w; so w=2*pi*f I presume that this is homework. You need to walk through the formulas and diagrams. This answer is right for this case, but the problem will occur again and you need to understand the fundamentals. Consider the divider formula Xc/(Xc+R) then 1/(1+R/Xc) compute the phase angle. Then draw the complex plane figures and see how you get the same answer. At some point the "meaning" will come through. It's there just look a little.

RRogers